CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A set of paper filters. The base texture is generated the same way, only the compositing mode is varied.
Source Lazur URH
No relation to the band, but damn it’s subtle!
Source Thomas Myrman
A seamless web texture of "green stone".
Source V. Hartikainen
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Clover with background for St. Patrick's Day. Add to a card with a doily, ribbon, a leprechaun or other embellishments.
Source BAJ
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
Prismatic Abstract Geometric Background derived from an image on Pixabay.
Source GDJ
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin